Parasitic Symphony

Gais Crispus once said, “Harmony makes small things grow, lack of it makes great things decay”. This quote conveys that the small things, which society looks beyond and belittles, are ultimately the foundation for greatness and complexity to occur. Carl Zimmer’s, Parasite Rex, explains how over time parasites have been classified as a negative aspect of nature, but in reality are the building blocks for earth’s biosphere. Mr. Zimmer takes the reader through a journey of when man first discovered parasites, the controversy behind their existence, and the various stages ­of a parasitic organisms life.

            Parasites have preceded man for thousands of years. The first civilization to make account of parasites was the Greeks. Along with Aristotle, they noticed groups of organisms living on the “tongue of swine, encased in cysts as hard as hailstones” (Zimmer 2). The Greeks also gave parasites their name, deriving from the Latin word, “parasitos”, literately meaning (beside food). At the time “parasitos”

(Zimmer 2) referred to officials that served at temple feasts. The officials hoped for a meal by keeping conversation or entertaining the wealthy guest(s). The etymological concept behind this is that “parasitos” hung around for an extensive amount of time. Not until years later did the term transfer over to biological reference for organisms that siphon nutrition from other animals.

            Not only were parasites new to human understanding but the question of religion played a role. After further questioning about how parasites came into existence scientists realized that parasites have never been seen outside the host’s body. Many specimens of animals were taken to try to uncover the mystery of where parasites are generated. “Fish, birds, any animal they dissected had different visible parasites, flukes, worms, and crustaceans” (Zimmer 5), living within their bodies. The best explanation for parasitic existence was that they were the aftermath of disease, giving the term spontaneous generation. Further studying went on and scientists discovered that parasites could even be found in the aborted fetuses of animals. At the time, spontaneous generation was considered heresy and a threat toward religion. As Plato was on trial for corrupting the minds of the youth in Euthyphro, it was only a matter of time before scientists were accused of doing the same. “The Bible taught that life was created by God in the first week of creation, and every creature was a reflection of his design and his beneficence” (Zimmer 8). Spontaneous generation contradicted the theory of creation because it seemed that our blood could produce life. If blood could generate life on its own then what help would parasites need from God?

            In the 1830’s Johann Steenstrup, a Danish Scientist was the first to propose, “parasites did[n’t] adhere to the rules of humans or animals” (Zimmer 36). Steenstrup made an outrageous suggestion. He proposed that parasites went through stages and generation of a single animal. For example the King’s Yellow Worm,

“The adults laid eggs, which escape out of their hosts and land in water, where they hatch into the form covered in fine hairs. The hair-covered form swims through the water and sought out a snail, and once it penetrates a snail, the parasite transforms itself into a shapeless bag. The shapeless bag begins to swell with the embryos of a new generation of flukes. But these new flukes are nothing like the leaf-shaped forms inside a sheep's liver, or even the finely haired form that entered the snail. These are the King's yellow worms. They moved through the snail, feeding and rearing within them yet another generation of flukes -- the missile-tailed cercariae. The cercariae emerged from the snail, promptly forming cysts on the snail. From there they somehow got into sheep or another final host (dispersal), and there they emerge from their cysts as mature flukes” (Zimmer 43). Along with

Steenstrup, many other scientists such as Leeuwenhoek, Koch, and Pasteur began to study parasitic habits. This in turn started the recognition of how extraordinary these organisms really were. Parasites could migrate throughout the entire body of another organism, they could manipulate the habits of the host, and some could even change the deoxyribonucleic acid of the invaded. Not only was this organism unlike any other in the animal kingdom but also in terms of “natural selection” (Strahler 289), it was one of the most complex and versatile animals in existence. This in turn enabled it to become an apex organism in terms of survival.

            Lastly, Zimmer’s intention was to differentiate the habitual way of thinking about parasites. He intended for us to look at them for the complexity that they entail, and the natural capabilities that they hold to survive. There is no wonder that they out number symbiotic organisms. What other organism can resist infection, bypass the immune system, manipulate another organism, or even influence the genetic makeup of another animal’s offspring? Carl Zimmer conveyed his purpose through this reading extremely well. Through the various examples and information given you can start to make your own assumptions about parasites that you wouldn’t of thought before. I learned that not only physical geography but also life in itself is about the small things. The small things are what make up the big things and give life complexity. Without the minuscule details everything would be a gray blob. This book truly makes you ponder about the creation of life and evolution through time. Parasite Rex is an extensive book and very detailed, but definitely a good read for reporting purposes. This reading makes you ask questions and rethink what you think you already know. “You see a thousand trees, but no forest”, Albert Einstein once said. All the biographic processes of a parasitic organism truly do orchestrate itself into a parasitic symphony.           




Strahler, A. (n.d.). Introducing Physical Geography (5th ed.). Danvers, MA: John                                              Wiley & Sons, Inc.

Zimmer, C. (2000). Parasite rex: inside the bizarre world of nature's most dangerous       creatures. New York, NY: Free Press. 


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